This invention relates to vehicle suspension systems, and more particularly to suspension systems which include coil springs.
A conventional type of vehicle suspension includes coils springs to aid in dampening the transmission of road inputs to the vehicle. Each coil spring is generally carried between spring seats of the vehicle's frame or body and the vehicle's control arm or axle.
The points of interface between vehicle suspension system components experience a great frequency of movement and are points at which work occurs during all types of vehicle operating conditions. A suspension experiences duty cycles comprised of jounces and rebounds in response to inputs from the surface the vehicle's tires interface with. Therefore, the suspension's performance has a direct impact on what the owner feels and hears from the vehicle and contributes significantly to the vehicle's "ride" characteristics.
A vehicle owner generally uses the vehicle in a variety of conditions and often becomes attuned to sounds and feels generated by the vehicle. This factor contributes to the ride characteristics perceived by the driver and passengers. It is desirable that a vehicle project an image of value and reliability. Therefore, attention is given to the areas such as the interface between the suspension coil springs and the vehicle spring seats with the goal of providing firm, secure and quiet performance of the vehicle's suspension system.
Objectionable sounds or noise can be generated by a vehicle's suspension due to metal-to-metal contact between system components caused by inadequate or nonexistent means of insulation. This has been found to be the case when coil springs are used in a vehicle's suspension. The end coils of a coil spring contact metal vehicle spring seats. During vehicle operation, relative movement occurs between the spring and the mating vehicle surfaces typically causing objectionable sound generation. It is conventional to use resilient insulators between the suspension's coil springs and its points of contact with the vehicle. However, it has been found that suspension systems which utilize coil springs with conventional insulators can exhibit a tendency to generate objectionable sounds.
It has been determined that conventional coil spring systems used in vehicle suspensions result in objectionable noise due to two root causes. First, a sufficient insulation contact area between the end coils and the spring seats may not be provided under all conditions of component part build variations. Second, the spring and mating vehicle components interact actively during suspension duty cycles which can cause known art insulators to become repositioned or torn. It has also been found that with conventional insulators corrosion may be facilitated by trapped water and corrosives, thereby contributing to objectionable noise generation.